Sen. Scott Brown (R-Mass.) gave $34,545 to the Autism Consortium in Boston as part of a deal between him and his presumed rival Harvard Law Professor Elizabeth Warren to discourage third-party ad spending in what could end up being the most expensive race in Massachusetts history.

The "People's Pledge," hammered out between the campaigns, seeks to limit the influence of outside money in the campaign. Under the terms, the candidates agreed to make a donation of one-half of the cost of a political ad buy by an outside group on his behalf.

The donation was triggered by an ad buy by the American Petroleum Institute urging constituents to tell Brown not to vote for a plan to eliminate tax subsidies to oil companies. Brown voted against the plan Thursday, which failed to meet the 60-vote threshold needed to end a filibuster.

The Warren campaign said the ads violated the pledge because Brown had voted in the past against ending the subsidies. Brown's campaign responded that the "issue ads" weren't in the terms but represented a "loophole" that needed to be closed and agreed to donate the money.

The donation is the second check Brown has written in violation of the pledge.

Brown and Warren remain deadlocked in the polls.

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